The invention relates in general to an electric cooling fan, for engines and in particular to an electric cooling fan for internal combustion engines of motor vehicles.
Electric cooling fans are used more and more in motor vehicles for technical and economical reasons, rather than using cooling ventilators which are directly and mechanically driven by the internal combustion engine, because the former are easier and more economically switched on and off. The present cooling fans, however, which remove built up heat within the internal combustion engine space of a motor vehicle, have a relatively high noise level which is recognized as especially disturbing in the slow-down phase of the cooling fan after the ignition has been turned off.
The German Published Unexamined Patent Application, DE-0S No. 21 21 053, describes an electro-cooling ventilator for combustion engines of motor vehicles, whereby an electromotor of the cooling ventilator runs continuously during the operation of the engine with a lower rotational speed, and a thermostatic switch bridges an additional resistor during increased cooling air requirements. This arrangement includes the resistor element as an additional resistance for lowering the rotational speed. However, this resistor element has a relatively large dimension and, therefore, requires additional space. Additionally, this arrangement is relatively expensive and exhibits additional problems concerning the cooling down.
It is, therefore, an object of this invention to provide an improved electric cooling fan for engines such as an internal combustion engine of motor vehicles.
It is further an object of the invention to provide an improved electric cooling fan having an electromotor and an additional resistor for purposes of reducing the noise emission during decreased cooling air requirement.
It is also an object to provide an electric cooling fan which requires less structural space, is more cost efficient, and does not require additional means for carrying-off excess heat.
The above and other objects are attained by an electric cooling fan arrangment having an electric motor. The motor is independently controllable by a thermostatic switch which is responsive to the temperature of the engine, generally taken from the engine coolant. The arrangement includes a resistive element which is detachably coupled to the motor for providing a torque reduction of the motor during periods of decreased air cooling requirements, which occur after the engine has been turned off. The rear window heater unit serves as the resistance element in the preferred embodiment.
The advantages of the invention are seen during periods of decreased cooling air requirement, and in particular during the removal of built-up or accumulated heat after the engine has been switched off. During these periods, the electromotor of the cooling ventilator runs with a lower rotational speed, and thereby produces less disturbing noises. By utilizing the existing rear window heater as drop resistor, an otherwise necessary resistor element is eliminated, since the rear window heater exhibits a range of resistance level suitable for a supplemental resistance. The initial purpose of the rear window heater, which today is present in practically all motor vehicles especially in passenger motor vehicles, has thereby been widened. Furthermore, the stray power released via the rear window heating unit, may be utilized for keeping the rear window free of eventual condensation.